The ornamental design for a portion of an automobile, as shown and described.
FIG. 1 is a front right perspective view of the portion of an automobile showing our new design;
FIG. 2 is a rear right perspective view thereof;
FIG. 3 is a front left perspective view thereof;
FIG. 4 is a rear left perspective view thereof;
FIG. 5 is a front view thereof;
FIG. 6 is a rear view thereof;
FIG. 7 is a right side elevation view thereof;
FIG. 8 is a left side elevation view thereof; and,
FIG. 9 is a top plan view thereof.
The bottom view forms no part of the claimed design. The portions of the automobile in light contrast are environment and form no part of the claimed design.